1. Field of the Invention
The present invention is related to a channel estimation device and related method of an orthogonal frequency division multiplexing system, and more particularly, to a channel estimation device and related method for tracking fast changing channel to improve the system efficiency.
2. Description of the Related Art
Currently, orthogonal frequency division multiplexing (OFDM) system is very common in wireless communication. Wireless channels usually are frequency selective and time varying, even the OFDM system has very good anti-frequency selective fading ability, it is still necessary to have a good channel estimation system at the receiving end to improve system efficiency. Especially when the system is in fast time varying wireless channel, the receiving end needs better dynamic channel estimation means to assistant the demodulation process for more correct OFDM signal to obtain better system efficiency.
Moreover, in prior art technology, in order to understand the unknown channel, pilot signals or training signals are usually added in the transmitted signals. The pilot signal is known signal information for the receiving end, therefore, at the receiving end the channel estimation can be performed with the pilot signal to obtain the information of the channel characteristics. When the pilot signal is added, in order to increase the transmission bandwidth, the pilot signal can only be used between few specific subcarriers in the OFDM, and the channel estimation can only perform channel characteristics estimation to these subcarriers. Afterward, these estimated subcarrier information is used to perform channel characteristics estimation to other subcarrier with non-pilot signal, and the method is usually is interpolation.
However, in the prior art technology, many channel estimation methods of the OFDM systems are developed under slow fading channel, and these systems are usually assumed as having small channel change during the time of several OFDM symbol time. Therefore, after the first channel estimation (usually using the training symbol to perform the channel estimation) before the next training symbol, the previous estimated channel characteristic can be used for data detection. Actually, in broadband wireless channel, the channel might have obvious change in one symbol of the OFDM. In the other words, different channel characteristics occur to two continuous symbols; by using the previous estimated channel to perform the data detection to the next symbol might cause huge error, which makes low efficiency of the system.
Therefore, it is desirable to provide a channel estimation device and related method of an orthogonal frequency division multiplexing system, to mitigate and/or obviate the aforementioned problems.